The invention pertains to a laser instrument for use in non-invasive or minimally invasive operations for the vaporization of biological tissue.
Laser instruments are used in combination with an endoscope for non-invasive or minimally invasive operations for the vaporization by contact of biological tissue, primarily in narrow-lumen hollow organs, for example, for transurethral tissue resection of the prostate in cases of benign prostatic hyperplasia. With one such laser instrument, known from EP 0 514 258 A1, the application cap fastened on the distal end of the laser light guide is bent, along with the light guide end, so that the laser irradiation emerges from the application tip in the form of a ray which is slanted at an angle to the axis of the instrument. In this regard, a danger exists that the application cap will drift in an uncontrolled fashion in the direction of the application tip during the treatment, i.e., laterally to the direction of movement, so that a target-precise, patient-friendly removal of tissue is made extremely difficult or even impossible within a closely surrounded treatment area.
Further, known from EP 0 433 464 B1 is a laser surgery applicator with a bent application tip which is topically coated with radiation-absorbing and light-scattering particles in order to obtain different treatment effects in individual surface sections of the applicator. Specifically, a more coagulating radiation treatment effect and a more cutting radiation treatment effect are obtained. The upward-bent application tip is illuminated on the surface areas on the outside of the bend primarily by diffuse light, so that a weak vaporization effect results there, and this applicator can thus be used for effective tissue ablation only to a very limited extent.
The objective of the invention is to provide a laser instrument similar to the types cited above that can perform effective biological tissue vaporization in both the prograde and the lateral directions relative to the instrument axis, and at the same time, can perform stabilization of the application cap during the tissue removal.
According to the invention, the above objective is achieved with a laser instrument that includes a special geometric configuration of the application cap. With this special geometric configuration of the application cap, the exit surface of the laser light bundle becomes significant. Namely, the laser light bundle becomes widened outward over the entire surface region o of the outer part of the bend at least as far as the outermost distal tip, but not over the radially outermost surface point of the bent part. As a result, with only a slight enlargement of the external dimensions of the application cap, an extremely effective vaporization of tissue is achieved. More specifically effective vaporization of tissue is achieved not just laterally, but also in the direction of the instrument axis, so that in addition to a long removal of tissue, a rechannelization of stenosed hollow organs is easily possible as well. Furthermore, the part of the bent applicator surface on the inner part of the bend is masked from the ray path of the laser light bundle. As a result of the distribution of vaporization and non-irradiated applicator sub-surfaces that is achieved, in combination with the sliding effect on the bent part, an automatic stabilization of the applicator cap is assured, and the danger of an uncontrolled vaporization of tissue or a adhering of tissue to the applicator tip is largely eliminated.
An especially advantageous aspect of the invention provides that at least the region of the bent part from which the ray emerges is roughened. As a result, when the laser instrument according to the invention is moved, small parts of the tissue to be vaporized are mechanically abraded and remain adhered to the roughened surface of the bent part. Under the effects of the laser irradiation, these tissue parts begin to carbonize, and the absorbed laser irradiation generates directly on the surface of the bent part a temperature which allows the tissue material coming into contact with the bent part to be vaporized rapidly.
Another advantageous aspect of the invention; is that the axial cap part is configured on the proximal end as the fiber core of the light guide with a receiving sleeve at a radial distance. This provides the advantage that the light guide is accommodated in a protected position within the applicator cap, while at the same time, a sure guiding of the laser light through the light guide to the distal end of the light guide is retained. In addition to that advantage, the light guide is preferably bonded to the proximal end of the receiving sleeve, and the receiving is designed as a thermal insulation zone according to the length of the sleeve. As a result, a high-strength mechanical coupling between the light guide and application cap is achieved. Furthermore individual heat-sensitive parts, such as the bonding location on the proximal end of the applicator, are effectively protected against overheating.
According to another aspect of the invention, the laser instrument is preferably used in conjunction with an endoscope, and the application cap is the guided in a sliding fashion within the working channel of the endoscope, so that pressure can be exerted on the tissue from the proximal end of the light guide and target-precise handling is made possible. In regard to this aspect of the invention, the length of the receiving sleeve is expediently dimensioned, not just from the standpoint of the thermal insulation zone, but also in such a way that the application cap is guided by means of the receiving sleeve over its entire motion path within the endoscope.
In terms of a high-quality optical coupling of the light guide and the application cap, the distal end of the light guide is expediently fused with the axial cap part. Furthermore, in order to minimize reflections on the light guide-applicator interface, the application cap and the fiber core of the light guide are expediently made of materials with the identical index of refraction and specifically for reasons of a high thermal loading capacity, preferably from quartz glass. For production reasons, the bent part is not continuously curved, but instead expediently runs at an angle to the axial cap part, and preferably, at a bending angle of between 5xc2x0 and 30xc2x0.
Because of its accurately controllable, patient-friendly vaporization effect, the laser instrument according to the invention can be used in many ways, but is used in an especially preferred way for transurethral prostate treatment, particularly in the case of benign prostatic hyperplasia.